It is known that a sheet conveyer of an image forming apparatus includes a main body and a movable body. The main body includes a main body guide and the movable body includes a movable body guide. The movable body is mounted movably from a guide position with respect to the main body. The sheet is guided in the guide position that is defined by the movable body guide and the main body guide. As one example, it has been known that an image forming apparatus includes a re-conveyer that re-conveys a sheet on which an image is formed by the image forming unit and that is reversed up-side-down. The re-conveyer conveys the reversed sheet to the image forming unit again. A conveyer unit including the re-conveyer is detachably mounted to the main body.